Federation conflicting types

[jurredejongh]

Hi all!

I am currently working on a POC with Apollo Federation, with multiple (federated) kotlin graphql servers. In 1 service, at startup, I get the following stacktrace. Apparently you can't use an extended type in a "normal" type? Is that correct?

Exception in thread "main" com.expediagroup.graphql.generator.exceptions.ConflictingTypesException: Conflicting class names in schema generation [class com.example.graphql.models.LogItem, class com.example.graphql.models.LogItem]
	at com.expediagroup.graphql.generator.internal.state.TypesCache.get$graphql_kotlin_schema_generator(TypesCache.kt:57)
	at com.expediagroup.graphql.generator.internal.state.TypesCache.get$graphql_kotlin_schema_generator(TypesCache.kt:45)
	at com.expediagroup.graphql.generator.internal.types.GenerateGraphQLTypeKt.objectFromReflection(generateGraphQLType.kt:53)
	at com.expediagroup.graphql.generator.internal.types.GenerateGraphQLTypeKt.generateGraphQLType(generateGraphQLType.kt:40)
	at com.expediagroup.graphql.generator.internal.types.GenerateGraphQLTypeKt.generateGraphQLType$default(generateGraphQLType.kt:36)
	at com.expediagroup.graphql.generator.SchemaGenerator.generateAdditionalTypes(SchemaGenerator.kt:123)
	at com.expediagroup.graphql.generator.SchemaGenerator.generateSchema(SchemaGenerator.kt:83)
	at com.expediagroup.graphql.generator.federation.FederatedSchemaGenerator.generateSchema(FederatedSchemaGenerator.kt:42)
	at com.expediagroup.graphql.generator.SchemaGenerator.generateSchema$default(SchemaGenerator.kt:73)
	at com.expediagroup.graphql.generator.federation.ToFederatedSchemaKt.toFederatedSchema(toFederatedSchema.kt:42)
	at com.expediagroup.graphql.generator.federation.ToFederatedSchemaKt.toFederatedSchema$default(toFederatedSchema.kt:38)

The models and query:

@KeyDirective(fields = FieldSet("id"))
data class Log(
    val id: Int,
    val logItems: List<LogItem>
)

@ExtendsDirective
@KeyDirective(fields = FieldSet("id"))
data class LogItem(
    @ExternalDirective val id: Int,
    val text: String
)

class LogQueryService : Query {
    fun getAll(): List<Log> {
        return listOf(
            Log(1, emptyList())
        )
    }
}

[smyrick]

You don't need to use the extends if the type is all in the same service. Where is the definition of LogItem that doesn't have the text field?

[jurredejongh]

The naming in my example might not be the best one, but LogItem is defined in another federated service. Log is defined in this service, that uses LogItem, but with the extra text field.

So there are 2 federated services, 1 is the graphql-kotlin server, the other is, for this example, a nodejs graphql server.

The graphql-kotlin server has the following schema:

type Log {
  id: Int!
  logItems: [LogItem!]!
}

extend type LogItem @key(fields: "id") {
  id: Int! @external
  text: String!
}

The nodejs graphql server has the following schema:

type LogItem @key(fields: "id") {
  id: Int!
  priority: Int!
}

I can't have the property logItems in the Log type because the graphql-kotlin service throws the exception I've included in my post, but it's a perfectly fine use case.

Am I missing something?

[smyrick]

Have you defined your Federated resolver?

https://expediagroup.github.io/graphql-kotlin/docs/schema-generator/federation/type-resolution

[jurredejongh]

I have. Something the type cache does not like when the class has the extends directive.. Without the extends directive it works perfectly fine. But unfortunately that is not my use case 😅

My complete code:

package com.example.features.graphql

import ...

@KeyDirective(fields = FieldSet("id"))
data class Log(
    val id: Int,
    val logItems: List<LogItem>
)

@KeyDirective(fields = FieldSet("id"))
@ExtendsDirective
data class LogItem(
    @ExternalDirective val id: Int,
    val text: String
)

class LogItemResolver : FederatedTypeResolver<LogItem> {
    override val typeName = "LogItem"

    override suspend fun resolve(
        environment: DataFetchingEnvironment,
        representations: List<Map<String, Any>>
    ): List<LogItem?> = representations.map { keys ->
        keys["id"]?.toString()?.toIntOrNull()?.let { id -> LogItem(id, "Temporary") }
    }
}

@Suppress("unused")
class LogQueryService : Query {
    fun getLog(): Log =
        Log(1, listOf(LogItem(2, "Text")))
}

The config:

val config = FederatedSchemaGeneratorConfig(
        supportedPackages = listOf("com.example.features.graphql"),
        hooks = CustomFederationGeneratorHooks(
            listOf(LogItemResolver())
        )
    )

And the exception:

Exception in thread "main" com.expediagroup.graphql.generator.exceptions.ConflictingTypesException: Conflicting class names in schema generation [class com.example.features.graphql.LogItem, class com.example.features.graphql.LogItem]
	at com.expediagroup.graphql.generator.internal.state.TypesCache.get$graphql_kotlin_schema_generator(TypesCache.kt:57)
	at com.expediagroup.graphql.generator.internal.state.TypesCache.get$graphql_kotlin_schema_generator(TypesCache.kt:45)
	at com.expediagroup.graphql.generator.internal.types.GenerateGraphQLTypeKt.objectFromReflection(generateGraphQLType.kt:53)
	at com.expediagroup.graphql.generator.internal.types.GenerateGraphQLTypeKt.generateGraphQLType(generateGraphQLType.kt:40)
	at com.expediagroup.graphql.generator.internal.types.GenerateGraphQLTypeKt.generateGraphQLType$default(generateGraphQLType.kt:36)
	at com.expediagroup.graphql.generator.SchemaGenerator.generateAdditionalTypes(SchemaGenerator.kt:123)

[jurredejongh]

Okay, update, so apparently I had a Ktor setting that breaks everything. When I got rid of io.ktor.development=true, everything worked again. Probably something with the class caching.